Press operated tapping apparatus



Dec. 29, 1964 J. H. oHME 3,162,873

PRESS OPERATED TAPPING APPARATUS Filed April 25 1962 2 Sheets--Sheei'l 1 Dec. 29, 1964 J. H. oHME 3,162,873 PREss OPERATED TAPPING APPARATUS Filed April 25, 1962 2 Sheets-Sheet 2 Iv VENT/:R2 l. H. HmE' United States Patent O 3,162,873 PRESS GPERATED TAPPING APPARATUS Joachim H. Ghme, East Orange, NJ., assignor to Western Electric Company, Incorporated, New York, N Y., a corporation of New York Filed Apr. 25, 1962, Ser. No. 190,026 4 Claims. (Cl. 10--129) This invention relates to thread tapping apparatus and particularly to improved tapping apparatus adapted for operation by apunch press.

While it is common practice in the manufacture of stamped parts having threaded holes, to stamp the parts with a punch press and then perform the tapping operation separately with .a drill press, other apparatus, such as disclosed in U.S. Patent 2,715,233 to K. Clark, have been developed to perform both stamping and tapping as part of a continuous punch press operation. With apparatus of the latter type, the linearly reciprocating motion of a punch press is transformed to rotary motion for driving a tap. This invention, however, proposes a self-leading tapping apparatus designed for utilization with a punch press wherein the tap spindle is free of any lead arrangement.

Clarks invention is primarily applicable to the production of large numbers of parts from coil or strip stock. In a mass production process, however, it is extremely desirable to maintain close control over the operation in order to prevent runs of defective parts and accordingly, this invention also proposes a self-leading tapping apparatus having means for detecting broken punches and taps. This invention provides a compact apparatus wherein the tap is resiliently mounted for safety reasons and to increase tap life and wherein the tap is readily accessible for replacement.

An object of this invention is a self-leading tapping apparatus adapted for operation by a punch press.

Another object of this invention is an improved tapping apparatus whereby the linearly reciprocating motion of a punch press is transformed to rotary motion for driving a spring-loaded tap.

Another object of this invention is a novel thread tapping apparatus to be utilized as part of a progressive punch `and die to economically and eiciently mass produce stamped parts with threaded holes.

A more specific object of this arrangement is a compact Vself-generating tapping apparatus adapted for use with a punch press having an improved tap design and improved means for detecting `broken punches and taps.

In accordance with the general features of this invention, a helically grooved element is retained at one end in a holder on a press ram. The other end of the element is journaled in a tapping head and geared to a similarly situated tapping setup. During operation of the punch press, the ram and holder with the connected tapping head move linearly downwards towards the workpiece until the linear movement of the head is halted by Contact with the workpiece. On the continued downstroke of the ram, rotational movement is imparted to the helically grooved element by suitable means, such as a ball screw assembly riding in the grooves. This rotary motion is transmitted through a gearing arrangement to drive a tap. The tapping spindle is spring loaded to permit the tap to retract if a blocked hole is encountered, thus preventing damage to the tap and possible injury to the operator. With this spring loaded design, no lead arrangement is necessary since the tap is self-leading. Lubricating means adjacent to the tap lubricate and cool the tap.

This invention embodies a ilexible design which may be utilized in combination with a Whistler type multiple setup or a progressive punch and die arrangement or may be used singularly if desired to tap one or more holes.

Since this apparatus is particularly suited for automatic production of parts with threaded holes from strip or coil stock, novel means are provided for detecting broken punches and taps in order to prevent runs. of defective parts.

Other objects and adavntages will be apparent when considered in conjunction with the following drawings, wherein:

FIG. 1 is a broken away side view of the invention taken along the line 1 1 in FIG. 3.

FIG. 2 is a view taken along the line 2-2 in FIG. 3; and,

FIG. 3 is atop view of the novel thread tapping apparatus.

With reference to the drawings, a helically grooved cylindrical rod 11 is journaled at one end in a conventional ball screw assembly 12 which is connected to a holder 13 on the upper die shoe 14 of a press ram (not shown). The ball screw assembly 12 is iixedly attached to the holder 13`by a screw connection wherein an upper threaded portion 16 of said assembly engages a threaded aperture 17 in the holder 13. When the threaded members 16 and 17 are fully engaged, a flanged portion 18 of the assembly locks ush against the holder 13 restricting its vertical movement and providing an additional bearing surface.

As the die shoe 14 moves downwards to an operating position, the reciprocating nut 19 transmits the punch press power to rotational tapping motion with minimal friction losses. To express it dierently, the ball screw assembly 12 :and the helical rod 11 which rides therein are the actuating elements of a self-generating tapping apparatus. No separate drive mechanism is required for the tap 21.

A flexible cover 22 surrounds the helical rod 11 and ball screw assembly 12 for environmental protection. The other end of the rod 11 is journaled between two thrust bearings 23 and 25 disposed in a tapping head 24. Since the bearing design and operation are well-known, a detailed discussion is omitted. Suflice it to say that with the conventional bearing arrangement 23, key 30 transmits the rotary motion of rod 11 to an integrally mounted oit-set gear 26. This gear 26 is in mesh with gear 27 which is situated about a tap spindle 2S in the head 24. The face of gear 27 is larger than the meshing face of gear 26 to maintain engagement during the vertical movement of the smaller gear.

In the illustrated embodiment, a guide rod 29 is mounted at one end in a guide 31 which rests on a shelf portion 32 of the holder 13. A bolt 33 on the end of the rod 29 rests on a shelf portion 34 of the guide 31 to provide the restraining action when the rod 29 is placed under tension. The opposite end of the rod 29 is journaled to a common-type single ball bearing unit 36. A threaded portion 37 passes through a section 38 of the housing 44, a nut 39 being provided to keep the rod 29 and bearing unit 36 in place when an upward force is applied. The tap 21 is held in a conventional collet 41 which is xedly retained in a member 43 by a threaded engagement for quick interchanging of taps. A gear stop 67 is provided to engage gear 26 and thereby hold member 43 stationary while the tap is being changed. A shoulder 45 of the member 43 rests on a ledge portion 50 of the housing 44. The member 43 is rotatably journaled in the housing element 44, which in turn is slidably mounted in the main tapping head 24, with a dog point screw 46 limiting the axial movement of the housing element 44.

Tap spindle 28 and tap 21 are resiliently loaded by means of the compressed spring 47 which is situated between holder 13 and housing section 38. This provides axial feeding motion for the tap 21 upon compression of the unit and no lead screw or Alead nut are necessary since the tap is self-leading, y Also, when the tap 21 encounters a high degree of resistance, it backs ofi against the urging ofthe spring 47.V This increasesitap lifeand protects the operator from shattered taps which might occur when the tap 21 encounters a part lacking a punched hole.

Return springs 48 are coiled about stripper bolts 4l? which are retained in the holder 13 resting on ledges 52 similar to the'guide rod arrangement 29. The opposite ends 42 are threaded and fixedly held in the head 24 by a set screw 51. The return springs 48' are normally under compression prior to the downward movement of the die shoe 14. During thedownwar'd movement of the ram, and after the head 24 has contacted the surface of the work, they are compressed still further. Thus, the springs 48 store the energy required to unwind the tap from the work on the upstroke of the ram.

In operation, the tappinghead 24, connected to the upper die shoe 14, approaches the work until the head 24 engages the work surface on the lower die shoe 15. Since holder 13 vis adapted for movement relative to the head 24, the downstroke of the die shoe 14 compresses springs 47 and 48 and transmits the vertical reciprocating motionV of the press to rotary motion of the Yhelix 11 through the ball screw assembly 12. Gear 26 on the helically grooved rod 11 turns meshing gear 27 to rotate the tap Zl'through its bearing arrangement 36. Feed spring 47 causes the rotating tap 21 which includes a spindle V28, held in collet 41 by a ball and socket arrangement 66, to advance into the prepunched holey 2l) of the workpiece 10l forming threads therein. Upon completion of the downward stroke, the upper die shoe 14 retracts and the rotation of the helix y11 is reversed` through the expansion of the compressed springs 4S, causing the tap 21 to unwind itself from the tapped hole.

When the tap 21 is completely unwound from the tapped hole of the work 10, the head of the stripper bolts 49 will have arrived on the ledge 52 of the holder 13, thus limiting further expansion of the return springs 48, and, consequently, stopping the rotary motion of helix 11, gears 2 6 and 27, and tap 21. Now head 24 will move upwards together with holder, 13 and die shoe 14, facilitating the removal of the work from under the tap and the feeding in of a new untapped workpiece. The time cycle for such removal and feeding of new work extends from the lifting yof the tapping head 24 from the work 1l) on the upstrolre, to the contact of head 24 with the work on the downstroke of the ram.

During tapping, an oil-air suspension is sprayed onto the tap 21 through Yaperture 53 from a lubricating source 54 actuated by the downward movement of the head 24 in order to cool the tap -21 and lubricate the work. Any standard method of chip removal such as a vacuum systern may be used to clear the work position.

To prevent runs of defective parts, a means for detecting broken taps 21 or punches (not shown) is included with the tapping apparatus.` A typical embodiment of such means comprises a spring actuated pilot rod 56 with anvend portion 57 situated in the holder 13 and an opposite end portion S8 extending through an aperture 59 in the tapping, head 24 to engage the tapped hole 35 on the downstroke of the press v(not shown). is slidably mounted in a unit 61 with (zo-operating resilient means 62. Normally the pilot 56 is located'in line with theltap 21 and one feed length distance away. When the pilot finds a hole closed because it either-'has not been punched or because a broken tap has been lodged therein, a switch 6.3 with a roller 64 riding Von the pilot rod is actuated to electrically uncouplev'the upper die shoe actuating means (not shown). The punch element or the tap 21 may then be replaced before the punch press is restarted. f

It is to be understood that this inventionvis not restricted to the tapping of individual parts since it read' ily lends itself to mass production operations.- vFor quantity runs it is possible to incorporate this invention with The rod 56 a progressive punch and die setup to automatically per'- form a variety of press-type operations and to turn out completed parts with tapped holes from a feed of coil '0f Strip stock- 'ThiS proposed tapping arrangement is particularlyfcompatible with automatic punch press op-l erations since the feed cycleand the Work Ycycle are synchronized with the punch presscycle, each occupying a maximum of one half the cycle. Y

It must also be mentioned that-this apparatus is'not limited to tapping a single hole but may be adapted to tap any number of yholes through gearing.` arrangements working off the gear. 26. A tapping apparatus of the type herein disclosed may be used with multiple Whistlertype setups where the konly limitation on the number of holes tapped is the spacing requirements. The embodiment selected for purposes .of illustrating the invention shows a compact design which is mechanically lockedA in the upper Vdieshoe 14 of a progressive punch and die through a dovetail-type shape `of the holder 13, for'pushin, pullout positioning. Such a design may be located at random beneath therarn of a punch press.

This invention lends itself to precise control of-the tapping operation rather than mere trial and error or empirical control. The ram `travel, ram velocity, tap speed, tap cutting speed and tap revolutionsfmay be pre'- determined with a high degree of accuracy from design relationships.V For example, the tap speed Y i: gear ratio of tapping head (Number of teeth, input gear) (Number of teeth, output gear) L=lead of drive helix (inches) t=time (seconds) y r=eccentricity of crank=.5 S1', (inches) Sp=stroke of press (inches) np=press speed (strokes per minute) therefore solving'for the tap speed ing:

Y thereon, a lower die shoe for 'supporting a part to be Vvthreaded, a ball screw assembly mounted on the holder having an aperture extending therethrough, a tapping head,

.a helically grooved cylindrical element having an upper portion riding in the aperture of the ball screw assembly, said elementrbeing rotatably driven Vby the assembly upon contact of the tapping head with the part,

a first gear mounted to the lower portion of the helically grooved element, v

V4bearing means in the tapping head having the geared end of the grooved element journaled therein,

a guide rod slidably mounted in the holder at one end,

a housing slidably mounted within the tapping head and y a reciprocatory upper die vshoe having a holder mounted 5 6 having the other end ofthe guide rod connected theremeans for readily detecting blocked holes in the parts, to, said means comprising a spring-actuated pilot rod a rotatable member journaled Within said housing and slidably mounted in the holder and positioned to enhaving a threaded internal aperture, gage tapped holes in the parts upon succeeding movea second gear mounted on said rotatable member and 5 ments of the press and means responsive to the pilot adapted to be driven by the first gear, said second gear rod indication or stopping the press when the rod having a wider tooth surface than the'rst gear to fails to engage a tapped hole. maintain engagement during reciprocatory movement 4. An apparatus in accordance with claim 1 further of the housing, including: a tap for engaging and forming threads in the part, 10 at least one stripper bolt slidably mounted in the means for mounting the tap Within the threaded aperholder at one end and xedly connected to the ture of the rotatable member, and tapping head at the other end, said bolt having resilresilient means disposed about the guide rod between ient means positioned thereabout between the holder the holderV and the housing for loading the tap. and the head to facilitate separation 'of the head from 2. An apparatus in accordance With claim 1 wherein: 15 the Work, and the rst gear comprises an offset gear mounted to the lubricating means for the tap responsive to the moveother end of the helically grooved element and jourment of the upper die shoe.

naled within the tapping head,

Y the rotatable member includes an upper portion de- References Cited m the me of thls patent signed to accommodate the thrust of the guide rod 20 UNITED STATES PATENTS and an intermediate shelf-like portion contacting a 2,221,598 McLaughHn NOV 12, 1940 Supporting surface of the housing, and 2,249,395 Reese 1111y 15, 1941 the tapping head includes a cavity within which the tap 2,314,138 Garbe et a1 Man 16, 1943 is normally recessed forA protection purposes and 2,346,297 Garbe APL 11, 1944 from which it projects to form threads upon contact 25 2,715,233 @1ark Aug 16, 1955 of the head with a part. 3. An apparatus in accordance with claim 1 further FOREIGN PATENTS including: 824,067 l' Great Britain Nov. 25, 1959 

1. AN APPARATUS FOR FORMING THREADS IN PARTS COMPRISING: A RECIPROCATORY UPPER DIE SHOE HAVING A HOLDER MOUNTED THEREON, A LOWER DIE SHOE FOR SUPPORTING A PART TO BE THREADED, A BALL SCREW ASSEMBLY MOUNTED ON THE HOLDER HAVING AN APERTURE EXTENDING THERETHROUGH, A TAPPING HEAD, A HELICALLY GROOVED CYLINDRICAL ELEMENT HAVING AN UPPER PORTION RIDING IN THE APERTURE OF THE BALL SCREW ASSEMBLY, SAID ELEMENT BEING ROTATABLY DRIVEN BY THE ASSEMBLY UPON CONTACT OF THE TAPPING HEAD WITH THE PART, A FIRST GEAR MOUNTED TO THE LOWER PORTION OF THE HELICALLY GROOVED ELEMENT, BEARING MEANS IN THE TAPPING HEAD HAVING THE GEARED END OF THE GROOVED ELEMENT JOURNALED THEREIN, A GUIDE ROD SLIDABLY MOUNTED IN THE HOLDER AT ONE END, A HOUSING SLIDABLY MOUNTED WITHIN THE TAPPING HEAD AND HAVING THE OTHER END OF THE GUIDE ROD CONNECTED THERETO, A ROTATABLE MEMBER JOURNALED WITHIN SAID HOUSING AND HAVING A THREADED INTERNAL APERTURE, A SECOND GEAR MOUNTED ON SAID ROTATABLE MEMBER AND ADAPTED TO BE DRIVEN BY THE FIRST GEAR, SAID SECOND GEAR 